CN113066958B - Current collector and application thereof - Google Patents

Current collector and application thereof Download PDF

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Publication number
CN113066958B
CN113066958B CN202110302054.3A CN202110302054A CN113066958B CN 113066958 B CN113066958 B CN 113066958B CN 202110302054 A CN202110302054 A CN 202110302054A CN 113066958 B CN113066958 B CN 113066958B
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current collector
layer
conductive layer
thickness
insulating layer
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CN113066958A (en
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翟艳云
张健
彭冲
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Zhuhai Cosmx Battery Co Ltd
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Zhuhai Cosmx Battery Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/665—Composites
    • H01M4/667—Composites in the form of layers, e.g. coatings
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Composite Materials (AREA)
  • Cell Electrode Carriers And Collectors (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The invention provides a current collector and application thereof. The current collector comprises an insulating layer, wherein at least one functional surface of the insulating layer is provided with a conducting layer, and the conducting layer comprises a first part close to the insulating layer; wherein the thickness of the first portion is greater than or equal to 20% based on the thickness of the conductive layer; wherein the density D of the first part is more than or equal to 50 percent; the roughness of the surface of the conducting layer far away from the insulating layer is 50nm-2 μm. The current collector has the advantages that at least 20% of the conducting layer with the thickness has higher density, so that the current collector has lower sheet resistance, and a lithium ion battery has better electrical property; the roughness of the surface of the conducting layer far from the insulating layer is large, so that the adhesion between the active layer and the conducting layer can be increased, the adhesion between the active layer and the current collector is increased, and the electrical property of the lithium ion battery is further improved.

Description

Current collector and application thereof
Technical Field
The invention relates to a current collector and application thereof, and belongs to the field of lithium ion batteries.
Background
The lithium ion battery is widely applied to the fields of mobile phones, notebook computers, electric automobiles and the like. With the increasing demand of various fields for battery capacity, specific energy and fast charging capability, people continuously challenge the design limit of materials and batteries, thereby making the safety defect of lithium ion batteries more obvious. In recent years, fire and explosion accidents of lithium ion batteries frequently occur, so that attention of all levels of society is attracted, and further application of the lithium ion batteries is restricted.
Conventional lithium ion batteries often use aluminum foil as a positive current collector and copper foil as a negative current collector. In the prior art, in order to improve the safety performance and energy density of the battery, a sandwich-structured composite current collector of aluminum foil-polymer layer-aluminum foil and copper foil-polymer layer-copper foil can be adopted to replace the aluminum foil and the copper foil. When the lithium ion battery is in short circuit, the polymer layer of the composite current collector is heated and shrunk, a short circuit loop is cut off, the lithium ion battery is prevented from thermal runaway, and the safety performance of the lithium ion battery is greatly improved. Furthermore, lighter weight polymer materials instead of part of the aluminum foil or copper foil also enable an increase in the energy density of the battery.
However, the loaded active layer of the composite current collector is easy to fall off from the surface of the current collector during the application process, which seriously affects the electrical performance of the lithium ion battery and limits the application of the composite current collector in the lithium ion battery.
Disclosure of Invention
The invention provides a current collector, which has good adhesion effect between the surface of the current collector and an active layer, can prevent the active layer from falling off, and improves the electrical property of a lithium ion battery.
The invention provides a pole piece, wherein an active layer on the surface of the pole piece is not easy to fall off.
The invention provides a lithium ion battery which is good in electrical property.
The invention provides a current collector, wherein the current collector comprises an insulating layer, at least one functional surface of the insulating layer is provided with a conducting layer, and the conducting layer comprises a first part close to the insulating layer;
wherein the thickness of the first portion is greater than or equal to 20% based on the thickness of the conductive layer;
the density D of the first part is more than or equal to 50 percent;
the roughness of the surface of the conducting layer far away from the insulating layer is 50nm-2 mu m.
The current collector as described above, wherein the conductive layer further comprises a second portion distal from the insulating layer;
wherein the thickness of the second portion is greater than or equal to 10% based on the thickness of the conductive layer;
the density of the second portion is less than the density of the first portion.
The current collector as described above, wherein the conductive layer comprises a first conductive layer and a second conductive layer, the first conductive layer disposed between the second conductive layer and the insulating layer;
the density of the first conducting layer is more than 50%, and the density of the second conducting layer is less than that of the first conducting layer.
The current collector as described above, wherein the thickness of the first conductive layer is equal to or greater than the thickness of the second conductive layer.
The current collector as described above, wherein a sum of a thickness of the first conductive layer and a thickness of the second conductive layer is 200nm to 5 μm.
The current collector as described above, wherein a sum of a thickness of the first conductive layer and a thickness of the second conductive layer is 700nm to 2 μm.
The current collector as described above, wherein the insulating layer has a thickness of 2 μm to 20 μm.
The current collector as described above, wherein the first conductive layer, the second conductive layer, and the insulating layer are provided with through holes in a thickness direction of the current collector.
The invention also provides a pole piece, wherein the pole piece comprises the current collector.
The invention also provides a lithium ion battery, wherein the lithium ion battery comprises the pole piece.
The current collector provided by the invention comprises an insulating layer, wherein at least one functional surface of the insulating layer is provided with a conducting layer, and the conducting layer comprises a first part close to the insulating layer; wherein the thickness of the first portion is greater than or equal to 20% based on the thickness of the conductive layer; the density D of the first part is more than or equal to 50 percent; the roughness of the surface of the conducting layer far away from the insulating layer is 50nm-2 mu m. The density of the conducting layer with the thickness of at least 20% of the current collector is higher, so that the current collector has lower sheet resistance, and the reduction of the internal resistance of a lithium ion battery is facilitated; the surface for arranging the active layer has larger roughness, which is beneficial to increasing the adhesive force between the active layer and the current collector and ensures that the lithium ion battery has good electrical property. In addition, the insulating layer in the current collector has the advantage of light weight, the mass energy density of the current collector can be improved, burrs are not easy to generate on the insulating layer, the safety performance of the lithium ion battery can be improved, and the insulating layer can shrink under the high-temperature condition, damage the current collector, cut off a current path of the lithium ion battery, and also improve the safety performance of the lithium ion battery.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the related art, the drawings used in the description of the embodiments of the present invention or the related art are briefly described below. It is obvious that the drawings in the following description are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.
Fig. 1 is a schematic structural view of a current collector according to a first embodiment of the invention;
fig. 2 is a schematic structural view of a current collector according to a second embodiment of the invention;
FIG. 3 is a schematic structural view of a pole piece in some embodiments of the present invention;
fig. 4 is a surface Scanning Electron Microscope (SEM) image of the first conductive layer in example 1 of the present invention;
FIG. 5 is an SEM image of a second conductive layer in example 1 of the present invention;
FIG. 6 is a schematic view of the structure of a core in example 1 of the present invention;
FIG. 7 is a schematic view of the structure of a core in example 2 of the present invention;
fig. 8 is a schematic structural view of a core in embodiment 3 of the present invention.
Description of reference numerals:
1: an insulating layer;
2: a first conductive layer;
3: a second conductive layer;
4: and an active layer.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a current collector, which comprises an insulating layer, wherein at least one functional surface of the insulating layer is provided with a conducting layer, and the conducting layer comprises a first part close to the insulating layer;
wherein the thickness of the first portion is greater than or equal to 20% based on the thickness of the conductive layer;
the density D of the first part is more than or equal to 50 percent;
the roughness of the surface of the conductive layer facing away from the insulating layer is 50nm-2 μm.
The functional surfaces in the present invention refer to two surfaces where the area of the insulating layer is largest and the two surfaces are oppositely disposed.
The compactness in the invention refers to the ratio of the theoretical sheet resistance of a metal material adopted by a conductive layer with the thickness of 1 micron multiplied by the thickness of the conductive layer to the actual sheet resistance of the conductive layer. The sheet resistance of the metal material of 1 micron thickness is commonly defined in the art as the theoretical sheet resistance. Generally, the theoretical sheet resistance of aluminum is 26.55m Ω/□, the theoretical sheet resistance of copper is 16.78m Ω/□, the theoretical sheet resistance of nickel is 68.4m Ω/□, the theoretical sheet resistance of silver is 15.86m Ω/□, the theoretical sheet resistance of gold is 24m Ω/□, and the theoretical sheet resistance of iron is 97.1m Ω/□.
Roughness in the present invention refers to the small pitch and the minute peak-to-valley unevenness of the surface of the conductive layer away from the insulating layer. The roughness of the present invention can be obtained by Atomic Force Microscope (AFM) testing.
In some embodiments of the present invention, the roughness of the surface of the second conductive layer 3 remote from the insulating layer is from 200nm to 800 nm. When the roughness of the second conducting layer 3 is too large, the uniformity of the electrical property of the battery is influenced, the roughness of the second conducting layer 3 is limited to be 200nm-800nm, under the condition, the uniformity of the electrical property can be ensured, meanwhile, the adhesion force between the active layer and the second conducting layer 3 is higher as much as possible, the adhesion force between the active layer and a current collector can be improved, and the electrical property of the lithium ion battery is improved.
Specifically, the material of the insulating layer includes, but is not limited to, polyethylene terephthalate (PET), polypropylene (PP), Polyethylene (PE), Polyimide (PI), polyether ketone (PEK), and Polyphenylene Sulfide (PPs).
Conductive layers include, but are not limited to, aluminum, copper, nickel, silver, gold, and iron. The materials of the conductive layers may be the same or different.
The current collector in the invention can be a positive current collector or a negative current collector.
The conductive layer with the thickness of at least 20% of the current collector has higher density, so that the current collector can have lower sheet resistance, and the internal resistance of the lithium ion battery is reduced. The surface of the conducting layer, which is far away from the insulating layer, has larger roughness, so that the adhesion between the active layer and the conducting layer can be improved, the adhesion between the active layer and the current collector is improved, and the lithium ion battery is ensured to have good electrical property. In addition, the insulating layer in the current collector has the advantage of light weight, the mass energy density of the lithium ion battery can be improved, the insulating layer can shrink at high temperature, the current collector can be damaged, a short circuit loop is cut off to improve the safety performance of the lithium ion battery, and the insulating layer is thin and is not easy to generate burrs, so that the safety performance of the lithium ion battery can be further improved. Therefore, the lithium ion battery prepared by the current collector has the advantages of good electrical property, low internal resistance, high energy density and good safety performance.
In order to reduce the sheet resistance of the current collector as much as possible and improve the electrical property of the lithium ion battery, the density of the first part can be more than or equal to 80%. The roughness of the surface of the conducting layer, which is far away from the insulating layer, is too large, which influences the uniformity of the electrical performance of the battery, and the roughness of the surface of the conducting layer, which is far away from the insulating layer, is limited to be 200nm-800 nm.
As known to those skilled in the art, the compactness of the conductive layer is inversely related to the surface roughness, so in order to ensure that the surface of the conductive layer away from the insulating layer has a greater surface roughness, in some embodiments of the present invention, the conductive layer further comprises a second portion away from the insulating layer;
wherein the thickness of the second portion is greater than or equal to 10% based on the thickness of the conductive layer;
the density of the second portion is less than the density of the first portion.
In the whole conducting layer, the thickness of the second part is at least 10%, so that the surface of the conducting layer, which is far away from the insulating layer, can be better ensured to have larger surface roughness, the adhesion between the active layer and the conducting layer can be improved, and the lithium ion battery is ensured to have good electrical property.
Fig. 1 is a schematic structural view of a current collector according to a first embodiment of the invention; fig. 2 is a schematic structural view of a current collector according to a second embodiment of the present invention. As shown in fig. 1 or fig. 2, in some embodiments of the present invention, the conductive layer includes a first conductive layer 2 and a second conductive layer 3, the first conductive layer being disposed between the second conductive layer and the insulating layer;
the density of the first conductive layer 2 is greater than 50%, and the density of the second conductive layer 3 is less than that of the first conductive layer 2.
It can be understood that the current collector of the present invention comprises an insulating layer 1, a first conductive layer 2 and a second conductive layer 3 from bottom to top, or comprises the second conductive layer 3, the first conductive layer 2, the insulating layer 1, the first conductive layer 2 and the second conductive layer 3 from bottom to top.
According to the invention, the first conducting layer 2 with high density is arranged on the surface of the insulating layer 1 of the current collector, so that the current collector has lower sheet resistance, the internal resistance of the lithium ion battery is reduced, and the electrical property of the lithium ion battery is improved.
It is to be noted that, when the conductive layer of the present invention is observed by a Scanning Electron Microscope (SEM), there is no distinct boundary between the first conductive layer and the second conductive layer.
In some embodiments of the present invention, the thickness of the first conductive layer 2 is equal to or greater than the thickness of the second conductive layer 3. In the invention, the thickness of the first conducting layer 2 is more than or equal to that of the second conducting layer 3, and the thickness of the high-density first conducting layer 2 is large, so that the sheet resistance of the current collector can be reduced, and the internal resistance of the lithium ion battery is reduced.
In some embodiments of the present invention, the sum of the thickness of the first conductive layer 2 and the thickness of the second conductive layer 3 is 200nm to 5 μm.
In the invention, when the thicknesses of the first conductive layer 2 and the second conductive layer 3 are too thick, conductive materials are wasted, the energy density of the lithium ion battery is reduced, and the safety performance of the lithium ion battery is also reduced; when the thicknesses of the first conductive layer 2 and the second conductive layer 3 are excessively low, mechanical properties of the current collector and electrical properties of the lithium ion battery are not facilitated. The invention limits the sum of the thickness of the first conducting layer 2 and the thickness of the second conducting layer 3 to be 200nm-5 mu m, and can improve the mechanical property of the current collector while ensuring the energy density and the safety performance of the current collector, thereby prolonging the service life of the lithium ion battery.
In some embodiments of the present invention, the sum of the thickness of the first conductive layer 2 and the thickness of the second conductive layer 3 is 700nm-2 μm. Under the condition, the safety performance, the electrical performance, the energy density and the mechanical performance of the current collector can simultaneously have more satisfactory effects.
In some embodiments of the present invention, the thickness of the insulating layer 1 is 2 μm to 20 μm.
In the present invention, when the insulating layer 1 is excessively thick, it results in low energy density of the battery; when the thickness of the insulating layer 1 is excessively low, the mechanical properties of the current collector and the safety performance of the battery are not facilitated. The thickness of the insulating layer 1 is limited to be 2-20 mu m, so that the current collector can have good mechanical property, excellent safety performance and high energy density.
In some embodiments of the present invention, the first conductive layer 2, the second conductive layer 3, and the insulating layer 1 are provided with through holes in the thickness direction of the current collector.
The mass energy density of the current collector can be increased by arranging the through holes in the thickness direction of the first conductive layer 2, the second conductive layer 3 and the insulating layer 1. Conductive materials can be filled in the through holes, so that double-side conduction of the current collector can be realized, and the conductivity of the current collector is improved.
The current collector of the invention can be prepared by a method comprising the following steps:
1) depositing a first conductive layer 2 on at least one functional surface of the insulating layer 1 using a first temperature and a first vacuum degree;
2) and depositing a second conductive layer 3 on the surface, far away from the insulating layer 1, of the first conductive layer 2 by adopting a second temperature and a second vacuum degree to obtain a positive current collector, wherein the second temperature is higher than the first temperature.
The first conductive layer 2 with high density can be formed at a lower deposition temperature and a higher vacuum degree, and the second conductive layer 3 with large surface roughness can be formed at a higher deposition temperature and a lower vacuum degree. In a specific embodiment, the first vacuum is 2 x 10 -4 Pa, the first temperature is 25-100 ℃, and the second vacuum degree is 2 x 10 -2 Pa, and the second temperature is 100-200 ℃.
The second aspect of the invention provides a pole piece, which comprises the current collector.
Fig. 3 is a schematic structural diagram of a pole piece in some embodiments of the invention. As shown in fig. 3, the pole piece of the present invention further comprises an active layer 4 disposed on at least one functional surface of the current collector. The positive plate can be obtained by arranging the positive active layer on the functional surface of the positive current collector, and the negative plate can be obtained by arranging the negative active layer on the functional surface of the negative current collector.
In the invention, the active layer 4 can be arranged on the surface of the second conducting layer 3 in the current collector, which is far away from the insulating layer 1, the active layer 4 is not arranged in a reserved partial area in the length direction of the current collector, and a tab is arranged in an area without the active layer 4; or arranging an active layer 4 on the whole surface of the second conductive layer 3 in the current collector, which is far away from the insulating layer 1, then removing part of the active layer 4 to expose the surface of the current collector, and arranging a tab on the exposed surface of the current collector; the surface of the second conducting layer 3 in the current collector, which is far away from the insulating layer 1, can be provided with an active layer 4, the reserved partial area in the width direction of the current collector is not provided with the active layer 4, and the area without the active layer 4 is subjected to die cutting to form a tab and then is connected with an outer tab.
The pole piece has low internal resistance, high adhesion between the active layer and the current collector and high safety performance.
The third aspect of the invention provides a lithium ion battery, which comprises the above pole piece.
In the invention, the positive plate, the diaphragm and the negative plate are laminated or wound to obtain the battery cell, the battery cell is placed in an outer package, and the lithium ion battery can be obtained by injecting electrolyte, formation, secondary packaging and capacity grading.
The separator may be a commercially available separator. The outer package may be an aluminum plastic film. The electrolyte may be a commercial electrolyte, and the electrolyte may include a lithium salt and a non-aqueous solvent. In the present invention, the lithium salt is not particularly limited, and any lithium salt known in the art may be used as long as the object of the present invention can be achieved. For example, the lithium salt may include LiPF 6 、LiBF 4 、LiAsF 6 、LiClO 4 、LiB(C 6 H 5 ) 4 、LiCH 3 SO 3 、LiCF 3 SO 3 、LiN(SO 2 CF 3 ) 2 、LiC(SO 2 CF 3 ) 3 Or LiPO 2 F 2 At least one of (1). In the present invention, the nonaqueous solvent is not particularly limited as long as the object of the present invention can be achieved. For example, the non-aqueous solvent may include at least one of a carbonate compound, a carboxylate compound, an ether compound, a nitrile compound, and other organic solvents.
The lithium ion battery provided by the invention comprises the electrode plate, so that the lithium ion battery has high energy density, low resistance and good safety performance.
The invention is further illustrated by the following specific examples in which all parts, percentages, and ratios recited in the following examples are by weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and used as such without further treatment, and the equipment used in the examples is commercially available.
Example 1
The lithium ion battery of the present example was prepared by the following steps:
1) preparation of positive current collector
Firstly, the vacuum degree is 2 x 10 -4 Under Pa, at a temperature of 30 DEG CDepositing a first conductive layer on both functional surfaces of the insulating layer, followed by a vacuum of 2 x 10 -2 Depositing a second conducting layer on the surface, far away from the insulating layer, of the first conducting layer at the temperature of 120 ℃ under the condition of Pa to obtain a positive current collector;
the insulating layer is made of polyethylene terephthalate (PET), the thickness of the insulating layer is 6 microns, the first conducting layer is made of aluminum, the density of the first conducting layer is 90%, the thickness of the first conducting layer is 800nm, the second conducting layer is made of aluminum, the surface roughness of the second conducting layer is 200nm, and the thickness of the second conducting layer is 300 nm.
Fig. 4 is a surface Scanning Electron Microscope (SEM) image of the first conductive layer in embodiment 1 of the present invention. As shown in FIG. 4, the first conductive layer deposited at 25-100 ℃ has smaller surface particles and higher compactness. Fig. 5 is an SEM image of the second conductive layer in embodiment 1 of the invention. As shown in fig. 5, the second conductive layer formed at 100-200 ℃ deposition has larger surface particles and larger surface roughness.
2) Preparation of positive plate
Dispersing a positive active material lithium cobaltate, a binder polyvinylidene fluoride (PVDF) and conductive carbon black in N-methyl pyrrolidone to obtain uniform positive active slurry, uniformly coating the positive active slurry on two surfaces, far away from an insulating layer, of a second conducting layer of the positive current collector prepared in the step 1), reserving a partial area in the length direction of the second conducting layer, not coating the positive active slurry, drying at 90-130 ℃ for 6 hours, rolling by using a roller press to obtain a positive active layer, and welding a tab in the area not coated with the positive active slurry to obtain a positive plate;
wherein the positive electrode active slurry comprises 97 wt% of lithium cobaltate, 2 wt% of PVDF and 1 wt% of conductive carbon black, and the thickness of the positive electrode active layer is 82 +/-3 mu m.
3) Preparation of negative plate
Dispersing graphite, styrene butadiene rubber serving as a binder, sodium carboxymethyl cellulose serving as a thickener and conductive carbon black serving as a conductive agent in deionized water to obtain negative active slurry, uniformly coating the negative active slurry on two surfaces of a copper foil, reserving a part of area in the length direction of the copper foil without coating the negative active slurry, drying for 6 hours at 90-130 ℃, rolling by a roller press to obtain a negative active layer, and welding a tab in the area without coating the negative active slurry to obtain a negative plate;
the negative active slurry comprises 97 wt% of graphite, 1.5 wt% of sodium carboxymethyl cellulose, 0.5 wt% of conductive carbon black and 1 wt% of styrene butadiene rubber, the solid content of the negative active slurry is 40-45 wt%, and the thickness of a negative active layer is 100 +/-3 mu m.
4) Preparation of lithium ion battery
Fig. 6 is a schematic structural view of a core in embodiment 1 of the present invention. As shown in fig. 6, the positive plate in step 2), the negative plate in step 3) and the diaphragm are wound to form a winding core, the winding core is placed in an outer package, electrolyte is injected, and the lithium ion battery is obtained through formation, secondary packaging and capacity grading.
Example 2
The preparation method of the lithium ion battery of the embodiment is basically the same as that of the embodiment 1, and the only difference is that:
in the step 2), the positive active slurry is coated on the whole surface of the second conductive layer, dried at 90-130 ℃ for 6 hours and rolled by a roller press to obtain a positive active layer, part of the positive active layer is removed, the surface of the second conductive layer is exposed, and a tab is welded on the exposed surface of the second conductive layer to obtain the positive plate.
And 3), coating the negative active slurry on the whole surface of a negative current collector, drying for 6 hours at 90-130 ℃, rolling by using a roller press to obtain a negative active layer, removing part of the negative active layer, exposing the surface of the negative current collector, and welding a tab on the exposed surface of the negative current collector to obtain a negative plate.
Fig. 7 is a schematic structural view of a core in embodiment 2 of the present invention. As shown in fig. 7, the positive plate in step 2), the negative plate in step 3) and the diaphragm are wound to form a winding core, the winding core is placed in an outer package, electrolyte is injected, and the lithium ion battery is obtained through formation, secondary packaging and capacity grading.
Example 3
The preparation method of the lithium ion battery of the embodiment is basically the same as that of the embodiment 1, and the only difference is that:
in the step 2), the positive active slurry is uniformly coated on two surfaces of a second conductive layer of the positive current collector, a reserved part of area in the width direction of the second conductive layer is not coated with the positive active slurry, tabs are die-cut in the area not coated with the positive active slurry, and then the tabs are welded with outer tabs to obtain the positive plate.
And 3) uniformly coating the negative active slurry on two surfaces of the copper foil, reserving a partial area in the width direction of the copper foil without coating the negative active slurry, die-cutting a tab in the area without coating the negative active slurry, and then welding the tab with an outer tab to obtain the negative plate.
Fig. 8 is a schematic structural view of a core in embodiment 3 of the present invention. As shown in fig. 8, the positive plate in step 2), the negative plate in step 3) and the diaphragm are wound to form a winding core, the winding core is placed in an outer package, electrolyte is injected, and the lithium ion battery is obtained through formation, secondary packaging and capacity grading.
Example 4
The preparation method of the lithium ion battery of the embodiment is basically the same as that of the embodiment 1, and the only difference is that:
the surface roughness of the second conductive layer in step 1) was 80 nm.
Example 5
The preparation method of the lithium ion battery of the embodiment is basically the same as that of the embodiment 1, and the only difference is that:
the density of the first conductive layer in the step 1) is 65%.
Example 6
The preparation method of the lithium ion battery of the embodiment is basically the same as that of the embodiment 1, and the only difference is that:
in the step 1), the insulating layer is provided with through holes in the thickness direction, and the ratio of the total area of the through holes to the area of the insulating layer is 10%.
Example 7
The preparation method of the lithium ion battery of the embodiment is basically the same as that of the embodiment 1, and the only difference is that:
in the step 3), coating the negative active slurry on the whole surface of the double-conductive-layer composite negative current collector, reserving a part of area in the length direction of the copper foil without coating the negative active slurry, drying for 6 hours at 90-130 ℃, rolling by using a roller press to obtain a negative active layer, and welding a tab in the area without coating the negative active slurry to obtain a negative plate;
the double-conductive-layer composite negative current collector is prepared by the following steps:
firstly, the vacuum degree is 2 x 10 -4 Depositing a first conductive layer on both functional surfaces of the insulating layer using a temperature of 30 ℃ under Pa, followed by a vacuum of 2 x 10 -2 Depositing a second conducting layer on the surface, far away from the insulating layer, of the first conducting layer at the temperature of 120 ℃ under the condition of Pa to obtain a double-conducting-layer negative current collector;
the insulating layer is made of polyethylene terephthalate (PET) and has a thickness of 6 microns, the first conducting layer is made of copper, the compactness of the first conducting layer is 91%, the thickness of the first conducting layer is 700nm, the second conducting layer is made of copper, the surface roughness of the second conducting layer is 300nm, and the thickness of the second conducting layer is 400 nm.
Example 8
The preparation method of the lithium ion battery of the present example is basically the same as that of example 7, and the only difference is that:
in the step 2), the positive active slurry is coated on two surfaces of a conventional aluminum foil with the thickness of 9 microns, dried for 6 hours at the temperature of 90-130 ℃, rolled by a roller press to obtain a positive active layer, and a tab is welded in the area which is not coated with the positive active slurry to obtain a positive plate.
Comparative example 1
The lithium ion battery of this comparative example was prepared essentially the same as example 1, except that:
the positive current collector in the step 2) is a conductive layer-insulating layer-conductive layer, the surface roughness of the conductive layer is 30nm, and the density is less than 50%.
Comparative example 2
The lithium ion battery of this comparative example was prepared essentially the same as example 1, with the only difference that:
the positive electrode current collector in the step 2) is a conventional aluminum foil.
Performance testing
1) Adhesion force
The pole pieces in the embodiment and the comparative example of the invention are laid on a desktop, transparent glue with the width of 24mm is adhered to the surfaces of the pole pieces, and sample pieces with the same width are cut by a blade along the length direction of the pole pieces. The cut sample piece was attached to an OPP film by a double-sided adhesive tape, and was back-pressed three times by a 2Kg press roll, and the adhesion was tested by a universal tester. The test results are shown in table 1.
2) Internal resistance test
The lithium batteries of the examples and comparative examples of the present invention were tested for internal resistance using an internal resistance tester model ZX 5563. The test results are shown in table 2.
3) Weight impact test
The lithium ion batteries of the examples and the comparative examples are fully charged, the lithium ion batteries are placed on a plane, a steel column with the diameter of 15.8 +/-0.2 mm is placed in the center of the lithium ion battery, the longitudinal axis of the steel column is parallel to the plane, a weight with the mass of 9.1 +/-0.1 kg is freely dropped onto the steel column above the lithium ion batteries from the height of 610 +/-25 mm, 20 lithium ion batteries obtained in the same example or the comparative example are tested in parallel, and the weight impact passing rate of the lithium ion batteries is calculated. The test results are shown in table 2.
4) Energy density calculation
The lithium ion batteries of the examples and comparative examples of the present invention were tested for capacity using a sort bin. The cell energy density is calculated by the formula energy density-capacity-voltage plateau/mass. The results are shown in Table 2.
Table 1, adhesion test results for the pole pieces of each example and comparative example
Figure BDA0002986649330000121
As can be seen from table 1, the adhesion of the pole pieces of examples 1-3 of the present invention is greater than that of the pole piece of comparative example 2. The adhesion of the electrode sheets of examples 1-3 to be less than that of comparative example 1 was determined by the conventional aluminum foil manufacturing process.
Table 2, performance test results of lithium ion batteries of examples and comparative examples
Item Internal resistance (m omega) Weight impact (pass/test) Energy Density (Wh/kg)
Example 1 41 20/20 305
Example 2 24 19/20 303
Example 3 10 17/20 298
Example 4 63 20/20 296
Example 5 52 20/20 298
Example 6 42 20/20 311
Example 7 52 20/20 323
Example 8 43 20/20 313
Comparative example 1 110 20/20 235
Comparative example 2 32 0/20 270
As can be seen from table 2, the internal resistance of the lithium ion batteries of examples 2 to 3 of the present invention is smaller than that of the lithium ion battery of comparative example 1, and the internal resistance of the lithium ion battery of example 1 is larger than that of the lithium ion battery of comparative example 1 because of the same tab connection manner, and the internal resistance of the composite current collector is larger than that of the aluminum foil.
The weight impact performance of the lithium ion battery of the embodiment 1-3 is better than that of the lithium ion battery of the comparative example 1, and the weight impact performance of the lithium ion battery of the comparative example 2 is better than that of the lithium ion battery of the embodiment 2-3, and is caused by the lug connection mode of the embodiment 2-3; the energy density of the lithium ion battery of the embodiment of the invention is greater than that of the lithium ion battery of the comparative example. Therefore, the lithium ion battery of the invention can ensure high energy density and improve the safety performance of the battery at the same time.
All the embodiments in the present specification are described in a related manner, and the same and similar parts among the embodiments may be referred to each other, and each embodiment focuses on the differences from the other embodiments.
The above description is only for the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall fall within the protection scope of the present invention.

Claims (10)

1. A current collector, comprising an insulating layer, wherein at least one functional surface of the insulating layer is provided with a conductive layer, wherein the conductive layer comprises a first portion adjacent to the insulating layer;
wherein the thickness of the first portion is greater than or equal to 20% based on the thickness of the conductive layer;
the density of the first part is more than or equal to 50 percent;
the roughness of the surface of the conducting layer, which is far away from the insulating layer, is 50nm-800 nm;
the conductive layer further comprises a second portion distal from the insulating layer;
wherein the thickness of the second portion is greater than or equal to 10% based on the thickness of the conductive layer;
the density of the second portion is less than the density of the first portion;
the materials of the conductive layers are the same.
2. The current collector of claim 1, wherein the conductive layer comprises a first conductive layer and a second conductive layer, the first conductive layer disposed between the second conductive layer and the insulating layer;
the density of the first conducting layer is more than 50%, and the density of the second conducting layer is less than that of the first conducting layer.
3. The current collector of claim 2, wherein the thickness of the first conductive layer is equal to or greater than the thickness of the second conductive layer.
4. The current collector of claim 2 or 3, wherein the sum of the thickness of the first conductive layer and the thickness of the second conductive layer is 200nm to 5 μ ι η.
5. The current collector of claim 4, wherein the sum of the thickness of the first conductive layer and the thickness of the second conductive layer is 700nm-2 μ ι η.
6. The current collector of claim 4, wherein the insulating layer has a thickness of 2 μ ι η to 20 μ ι η.
7. The current collector of any one of claims 1 to 3 or 5, wherein the insulating layer has a thickness of 2 μm to 20 μm.
8. The current collector of any one of claims 2, 3, 5, and 6, wherein the first conductive layer, the second conductive layer, and the insulating layer are provided with through holes in a thickness direction of the current collector.
9. A pole piece comprising the current collector of any one of claims 1 to 8.
10. A lithium ion battery, characterized in that it comprises a pole piece according to claim 9.
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